von Willebrand factor (VWF) is a blood glycoprotein involved in hemostasis. It is deficient and/or defective in von Willebrand disease and is involved in many other diseases, including thrombotic thrombocytopenic purpura, Heyde's syndrome, and possibly hemolytic–uremic syndrome. Increased plasma levels in many cardiovascular, neoplastic, and connective tissue diseases are presumed to arise from adverse changes to the endothelium, and may predict an increased risk of thrombosis
Structure
Multimers of VWF can be extremely large, >20,000 kDa, and consist of over 80 subunits of 250 kDa each. Only the large multimers are functional. Some cleavage products that result from VWF production are also secreted but probably serve no function.
Function
Von Willebrand Factor's primary function is binding to other proteins, in particular factor VIII, and it is important in platelet adhesion to wound sites. It is not an enzyme and, thus, has no catalytic activity.
VWF binds to a number of cells and molecules. The most important ones are:
Factor VIII is bound to VWF while inactive in circulation; factor VIII degrades rapidly when not bound to VWF. Factor VIII is released from VWF by the action of thrombin. In the absence of VWF, factor VIII has a half-life of 1-2 hours; when carried by intact VWF, factor VIII has a half-life of 8-12 hours. VWF binds to collagen, e.g., when collagen is exposed beneath endothelial cells due to damage occurring to the blood vessel. Endothelium also releases VWF which forms additional links between the platelets' glycoprotein Ib/IX/V and the collagen fibrils VWF binds to platelet gpIb when it forms a complex with gpIX and gpV; this binding occurs under all circumstances, but is most efficient under high shear stress (i.e., rapid blood flow in narrow blood vessels, see below). VWF binds to other platelet receptors when they are activated, e.g., by thrombin (i.e., when coagulation has been stimulated).
VWF plays a major role in blood coagulation. Therefore, VWF deficiency or dysfunction (von Willebrand disease) leads to a bleeding tendency, which is most apparent in tissues having high blood flow shear in narrow vessels. From studies it appears that VWF uncoils under these circumstances, decelerating passing platelets. Recent research also suggests that von Willebrand Factor is involved in the formation of blood vessels themselves, which would explain why some people with von Willebrand disease develop vascular malformations (predominantly in the digestive tract) that can bleed excessively.
Young Research Forum: Advances in Robotics & Automation
Young Research Forum: Advances in Robotics & Automation
Editorial: Advances in Robotics & Automation
Editorial: Advances in Robotics & Automation
Short Communication: Advances in Robotics & Automation
Short Communication: Advances in Robotics & Automation
Review Article: Advances in Robotics & Automation
Review Article: Advances in Robotics & Automation
Editorial: Advances in Robotics & Automation
Editorial: Advances in Robotics & Automation
Editorial: Advances in Robotics & Automation
Editorial: Advances in Robotics & Automation
Posters-Accepted Abstracts: Biosensors & Bioelectronics
Posters-Accepted Abstracts: Biosensors & Bioelectronics
: International Journal of Sensor Networks and Data Communications
: International Journal of Sensor Networks and Data Communications
Posters-Accepted Abstracts: Journal of Material Sciences & Engineering
Posters-Accepted Abstracts: Journal of Material Sciences & Engineering
Scientific Tracks Abstracts: Industrial Engineering & Management
Scientific Tracks Abstracts: Industrial Engineering & Management
Accepted Abstracts: Journal of Material Sciences & Engineering
Accepted Abstracts: Journal of Material Sciences & Engineering
Scientific Tracks Abstracts: Journal of Material Sciences & Engineering
Scientific Tracks Abstracts: Journal of Material Sciences & Engineering
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